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Author Topic: Ascraft Cinex Lamps and Rectifiers Stephen Furley Film God Posts: 3059 From: Coulsdon, Croydon, England Registered: May 2002 posted 09-17-2014 07:00 AM                     Dave, I doubt that it would have been for transit, I don't think that they ever took d.c. from the public supply, but used their own rotary converters or rectifiers. The New York Subway only shut down its last 25 Hz. rotaries in about 1999, and the IND had some more modern 60 Hz. ones for a little longer. For d.c. public supply in a city my best guess would be lifts (elevators) in older buildings. Cranes in industrial premises or dockyards would be another possibility.  |  IP: Logged Kenneth Wuepper Phenomenal Film Handler Posts: 1026 From: Saginaw, MI, USA Registered: Feb 2002 posted 09-17-2014 07:08 AM                     Many years ago the electrical generation plant in Grayling, Michigan was a few city blocks from the theatre. The Diesel generator, in addition to the AC power, supplied DC to the projection booth where the ballasts limited current for the Carbon lamps. The operator demonstrated how holding the Carbons together could dim the street lights outside. Now that was really fun!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 09-17-2014 09:52 AM                     For many years IATSE required only DC for stage lighting on broadway  |  IP: Logged David Buckley Jedi Master Film Handler Posts: 525 From: Oxford, N. Canterbury, New Zealand Registered: Aug 2004 posted 09-17-2014 05:08 PM                        quote: Dave Macaulay A decade or so back there was still some DC service in New York City that you could trace in the street with a compass. I have no idea what used it, maybe transit? I can remember when it was switched off, it was quite a big deal. What was it used for: Elevators. It is only of comparatively recent times with the development of variable speed drives (VSDs) that elevators with AC motors could have both have their speed controlled smoothly, and be capable of high speed. Which were the attributes necessary in tall buildings. Before the development of VSDs, one had to use DC motors. To run those DC motors, one needed (obviously) DC. Where there wasn't a DC supply, the best way to control elevators nicely was using the Ward Leonard system, but that needed a lot of heavy equipment (it was based on motor-generators), and was quite inefficient. quote: Gordon McLeod For many years IATSE required only DC for stage lighting on broadway I've read about DC lighting being used in books, but never actually seen it myself. DC based control systems (some of them are, quite literally, Frankenstein boards) still exist in a number of theatres, long unused. But... the same advances in electronics that made VSDs possible also brought the stage lighting equivalent, the SCR (originally thyristor, later triac) dimmers. This invention was the single greatest advance in stage light ever, and swept away all before it. That was the end of DC in theatre.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 09-18-2014 01:39 PM                     If Esther Williams ever knew how they lit those underwater scenes in her movies, she'd probably shit a brick! They just threw a light bulb into the pool and let the water carry the DC current back to ground.  |  IP: Logged Rick Raskin Phenomenal Film Handler Posts: 1100 From: Manassas Virginia Registered: Jan 2003 posted 09-18-2014 02:35 PM                     The telephone plant runs on DC. Commercial AC feeds rectifiers which continuously charge batteries that float on the system. In the event of a commercial power failure the batteries continue to supply power until backup generators come online. Essential AC is produced by inverters that run on DC. There are some gargantuan Frankenstein switchboards in those power rooms. I remember in one CO seeing the ammeter register in excess of 6000 amps. One CO complex in Washington DC had 5 750KW turbines for backup but I'm told those have since been replaced with diesels. Most of the theaters in that area ran MG sets for DC but I do remember there was commercial DC in a small area in the 1960s. The old trolley system generated their own DC and I recall as a kid being fascinated by the power plant that was on Georgia Ave.  |  IP: Logged

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